1. Field of the Invention
The present invention relates, in general, to methods of manufacturing toothbrushes with needle-shaped bristles and toothbrushes manufactured using the methods and, more particularly, to a method of manufacturing a toothbrush with needle-shaped bristles which enhances the workability thereof, and a toothbrush with needle-shaped bristles having improved penetration ability and flexibility.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Generally, needle-shaped bristles, which have sharp ends and are set in a toothbrush, have superior flexibility and the ability to penetrate into gaps between teeth or into periodontal pockets, compared to normal bristles with end points which are round. Thus, recently, needle-shaped bristles have been set in almost all high quality toothbrushes.
In methods of manufacturing such needle-shaped bristles, there are methods: (i) in which end points of bristles are dissolved using a strong alkali chemical or strong acid chemical, (ii) in which bristles are ground using a grinder after a bristle setting process has been conducted, and (iii) in which bristles are partially tapered using the method (i) and are then additionally grounded using the method (ii).
High quality needle-shaped bristles, which are tapered such that the length of the tapered portions of the bristles are relatively long, that is, 5 mm or longer, and the thickness of end points of the bristles are approximately 0.01 mm, can be produced through the method (i). Because the tapered portions of these needle-shaped bristles are relatively long, the flexibility thereof increases. Furthermore, the end points of the bristles are relatively thin, so that the penetration ability is superior. However, it is very difficult to adjust the precise time required to dissolve the bristles. Also, there is the problem of an increased number of defective products.
In the case of the method (ii), the workability is increased, but because tapered portions of produced needle-shaped bristles are relatively short, that is, 2 mm, the flexibility is poor. As a result, there is a problem of damage to the gums of a user.
The method (iii) is advantageous in that it solves some problems of the methods (i) and (ii). This method (iii) was proposed in Korean Patent No. 261658 and Korean Patent No. 421454, which were filed by the inventor of the present invention. Korean Patent No. 261658 proposes a method, in which bristles are immersed and dissolved in a strong acid chemical or a strong alkali chemical until just before the length of the bristles is reduced and, thereafter, the partially tapered bristles are washed in water and dried, and then set in a head part of a toothbrush after being ground using a grinder. The needle-shaped bristles produced by this method are relatively long, that is, approximately 5 mm, so that the flexibility thereof is superior. However, because the thickness of the end points of the bristles ranges from 0.04 to 0.08 mm, that is, because the thickness of the end points is relatively large, the penetration ability is poor. If the grinding process is further conducted to reduce the thickness of the end points of the bristles, the length of the tapered portions of the bristles is reduced, thus resulting in poor flexibility.
Korean Patent No. 42154 is similar to Korean Patent No. 261658. In this case, bristles are ground such that the thickness of end points of bristles is 0.02 mm or less in order to enhance the penetration ability. However, this case is problematic in that, because the length of tapered portions of the bristles ranges from 2.8 to 3.5 mm, the flexibility is poor. Furthermore, there is a problem in that the number of defective products increases in this manufacturing process.
That is, it has been very difficult to produce needle-shaped bristles having both increased penetration ability and flexibility through the conventional immersion and grinding processes.